I'm currently planning to get a VPS from VPS.net for a PHP project. I personally haven't used CentOS (which is recommended all the time) and this is not a good time for me to start learning it, so I want to stick with Ubuntu, as that's the one I have experience with. Now there's the good ol' 8.04 LTS that's well supported, however, 10.04 LTS was released two days ago. I installed it on my laptop and it is pretty slick (doesn't matter for a server) and quick. But I am skeptical about it:

I have jumped onto 10.04 on 3 different machines (different hardware architectures - workstation, laptop, netbook) and found that there are a number of little things that make it lack polish - no show stoppers though. That said, I would recommend waiting a couple of months for them to iron out all the kinks.

I've a production MTA (postfix, amavis, spamassassin, clamav & AD Integration) running on Ubuntu 10.04 server, and as yet (touch wood), I've not seen any issues.

I'm planning to upgrade all our Ubuntu servers to 10.04 LTS, as they are all currently running unsupported versions of the OS, however my hand was forced early with this system, as it had just started playing up, so I figured I'd bite the bullet and give it a try.

Whilst installing the system, I used a dokuwiki instance to document every step of the installation process (as per ptman's answer), then if I did have problems, I could easily re-install the system on 8.04.

I upgraded my 10.04 desktop over my 8.04 desktop and 10.04 died on the reboot because it couldn't find network sockets. I tried the 10.04 CD and it couldn't get past the router either. Meanwhile 8.04 works fine.

I know its not the same as a server but my advice is DON'T BELIEVE THE HYPE. 8.04 works. Stick with it.